Microscopes have assisted scientists and researchers for hundreds of years. From chemistry to the construction of computer chips to genetics to medical research, nearly every imaginable discipline has benefited from the ability to magnify the very small.
The oldest of microscopes were optical in nature, and were comprised of little more than a few lenses and a light source. These microscopes use the visible wavelengths of light to observe the microscopic. Over time, such optical microscopes have become more and more complex using dozens of lenses and reflecting/refracting elements. Medical researchers often use optical microscopes, as they allow living specimens to be observed without causing harm to the specimens. Today, such optical microscopes are considered to have a “theoretical limit” of resolution of about 200 nanometers—more precisely, 187 nanometers—because of the resolution limitations of lenses, the limited wavelengths of visible light, and limitations on the angular apertures of lenses. Thus, things smaller than approximately 0.2 microns are not readily viewable through standard optical microscopes. Even when viewing features at this lower resolution limit, some contrasts and color are often lost.
More recent developments in microscopy have resulted in electron microscopes, which use beams of electrons instead of beams of light. As electrons can be accelerated to produce a much smaller wavelength than visible light, electron microscopes allow much higher resolution than standard optical microscopes.
However, while electron microscopes can resolve features less than 0.2 microns, they typically cannot be used on living specimens. Electron microscopes use very high energy electron beams which can be harmful to living specimens. Also, to be viewed by an electron microscope, each specimen must be placed in a vacuum for viewing, as a gas would improperly scatter the electron beam, which vacuum would cause the death of a living specimen. Further, electron microscopes are often quite expensive to purchase and maintain, and require special power sources and a stable building.
Therefore, it would be preferable to combine the higher resolution qualities of an electron microscope with the lower expense and the ability to view living specimens of an optical microscope. It would further be preferable to view true color and high contrast images through an optical microscope.